7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Study of Multi-Scale Turbulence in the Core of Electron-Heating-Dominant Hmode Plasmas on EAST

P. J. Sun1, Y. Ren2, H. Q. Liu1, W. X. Wang2, Y. D. Li1, X. F. Han1, H. S. Cai3, G. S. Li1, Y. F.
Wang1, B. L. Hao1, Y. F. Jin1, S. Y. Fu1, H. L. Zhao1, Y. M. Duan1, L. Q. Xu1, J. Huang1, R. Ding1, J.
P. Qian1, L. Wang1, Q. Zang1, X. Z. Gong1, X. D. Zhang1, G. S. Xu1, J. S. Hu1, Y. T. Song1 andEAST team1
1
Institute of Plasma Physics, Chinese Academy of Sciences, 2 Princeton Plasma Physics
Laboratory, 3 University of Science and Technology of Chinae-mail (speaker): sunpj@ipp.ac.cn
Electron thermal transport is particularly important due tothe dominance of electron heating by the fusion-born
alpha particles in future magnetic confined burning
plasmas [1-6]. H-mode is a high confinement regime
which can fulfil the requirement of Q>1 plasma fusion
scenarios in ITER and BEST. As important candidates todrive electron thermal transport, the study of TEM andETG electron-mode turbulence as well as their transportfeatures is necessary and important, especially in electronheating-dominant H-mode plasmas. In this talk, coreregion multi-scale density fluctuation from low-k to highk have been investigated in an electron-heating-dominant
ELM-free H mode plasmas (H98, y2~1) under the auxiliary
heating of ECRH and NBI on EAST. Low-k density
fluctuation with k< 5 cm^-1 (kρi ≤ 2) and high-k density
fluctuation with k=10 (kρi ≤ 4), 20 cm^-1 (kρi ≤ 8) inthe plasma core were measured by the EAST
reflectometer diagnostic and CO2 laser collective
scattering diagnostic, respectively. Transient suppressionof density fluctuation has been found across the L-Htransition phase. After that, obvious increase of density
fluctuation power in all these wavenumbers (see Figure 1)
is observed for more than 500 ms following with theplasma ELM-free phase. Gyrokinetic simulations havebeen carried out to analyze the dominant microinstabilities in the turbulence measurement region for theELM-free phase using the GS2 code. Both TEM and ETG
modes are identified to be unstable for ρ < 0.5, which isconsistent with the obvious power of low-k and high-k
density fluctuation observed in experiment. Moreover,the critical temperature gradient (R/LTe)c for the onset of
the ETG modes also has been calculated using the GS2
codes. The direct comparison of (R/LTe)c withexperimental (R/LTe) supports the observation of obvious
high-k turbulence in experiment. Power balance analysis
also has been performed by using the TRANSP code.
Nonlinear simulations of TEM turbulence are ongoingwith the gyrokinetic simulation code GTS.

*This work is supported by National Natural Science
Foundation of China under grant Nos. 12275316 and11875286, and the Open Fund of Magnetic Confinement
Fusion Laboratory of Anhui Province under Grant No.
2022AMF02001.
References[1] Y. Ren et al., Phys. Rev. Lett. 106, 165005 (2011).
[2] E. Mazzucato et al., Phys. Rev. Lett. 101, 075001 (2008).
[3] W. X. Wang et al., Phys. Rev. Lett. 106, 085001 (2011).
[4] W. X. Wang et al., Phys. Rev. Lett. 87, 055002 (2009).
[5] Y. Ren et al., Nucl. Fusion 57, 072002 (2017).
[6] S. Mazzi et al., Nature Physics 18, 776-782 (2022)

Figure 1. Frequency spectrum of (a) k=10 cm−1 and (b)k=20 cm − 1 density fluctuation measured by CO2 laser
collective scattering diagnostic. Turbulence power Stot
(i.e., frequency integrated spectral power) of (a) k=10 cm−1and (b) k=20 cm−1 density fluctuation.